Campbell BlackGlobe User manual

BlackGlobe Temperature
Sensor for Heat Stress
Revision: 9/13
Copyright © 2013
Campbell Scientific, Inc.

Warranty
“PRODUCTS MANUFACTURED BY CAMPBELL SCIENTIFIC, INC. are
warranted by Campbell Scientific, Inc. (“Campbell”) to be free from defects in
materials and workmanship under normal use and service for twelve (12)
months from date of shipment unless otherwise specified in the corresponding
Campbell pricelist or product manual. Products not manufactured, but that are
re-sold by Campbell, are warranted only to the limits extended by the original
manufacturer. Batteries, fine-wire thermocouples, desiccant, and other
consumables have no warranty. Campbell’s obligation under this warranty is
limited to repairing or replacing (at Campbell’s option) defective products,
which shall be the sole and exclusive remedy under this warranty. The
customer shall assume all costs of removing, reinstalling, and shipping
defective products to Campbell. Campbell will return such products by surface
carrier prepaid within the continental United States of America. To all other
locations, Campbell will return such products best way CIP (Port of Entry)
INCOTERM® 2010, prepaid. This warranty shall not apply to any products
which have been subjected to modification, misuse, neglect, improper service,
accidents of nature, or shipping damage. This warranty is in lieu of all other
warranties, expressed or implied. The warranty for installation services
performed by Campbell such as programming to customer specifications,
electrical connections to products manufactured by Campbell, and product
specific training, is part of Campbell’s product warranty. CAMPBELL
EXPRESSLY DISCLAIMS AND EXCLUDES ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE. Campbell is not liable for any special, indirect,
incidental, and/or consequential damages.”

Assistance
Products may not be returned without prior authorization. The following
contact information is for US and international customers residing in countries
served by Campbell Scientific, Inc. directly. Affiliate companies handle
repairs for customers within their territories. Please visit
www.campbellsci.com to determine which Campbell Scientific company serves
your country.
To obtain a Returned Materials Authorization (RMA), contact CAMPBELL
SCIENTIFIC, INC., phone [phone]. After an applications engineer
determines the nature of the problem, an RMA number will be issued. Please
write this number clearly on the outside of the shipping container. Campbell
Scientific’s shipping address is:
CAMPBELL SCIENTIFIC, INC.
RMA#_____
815 West 1800 North
Logan, Utah 84321-1784
For all returns, the customer must fill out a “Statement of Product Cleanliness
and Decontamination” form and comply with the requirements specified in it.
The form is available from our web site at www.campbellsci.com/repair. A
completed form must be either emailed to [e-mail] or faxed to
[phone]. Campbell Scientific is unable to process any returns until we
receive this form. If the form is not received within three days of product
receipt or is incomplete, the product will be returned to the customer at the
customer’s expense. Campbell Scientific reserves the right to refuse service on
products that were exposed to contaminants that may cause health or safety
concerns for our employees.

Table of Contents
PDF viewers: These page numbers refer to the printed version of this document. Use the
PDF reader bookmarks tab for links to specific sections.
1. Introduction.................................................................1
2. Cautionary Statements...............................................1
3. Initial Inspection .........................................................1
3.1 Ships With List.....................................................................................1
4. Overview......................................................................2
5. Specifications .............................................................2
5.1 Accuracy ..............................................................................................2
6. Installation...................................................................4
6.1 Siting ....................................................................................................4
6.2 Assembly and Mounting ......................................................................4
6.2.1 Mounting the BlackGlobe on the Mounting Arm .........................4
6.2.2 Mounting the BlackGlobe Assembly on a Horizontal
Crossarm....................................................................................6
7. Operation.....................................................................7
7.1 Wiring ..................................................................................................7
7.2 Calculations..........................................................................................8
7.2.1 Wet-Bulb Globe Thermometer Index (WBGT) ............................8
7.2.2 Dewpoint.......................................................................................8
7.2.3 Vapor Pressure ..............................................................................9
7.2.4 Saturated Vapor Pressure ..............................................................9
7.2.5 Wet-Bulb.......................................................................................9
7.2.6 Mean Site Barometric Pressure Calculation (SP_kPa)................10
7.3 Programming......................................................................................10
7.3.1 Example CR1000 Program .........................................................10
7.4 Long Lead Lengths ............................................................................12
8. Maintenance ..............................................................12
9. References ................................................................12
i

Table of Contents
ii
Appendices
A. The Theory of BlackGlobe Temperature and
Heat Stress ............................................................A-1
B. Edlog Programming Examples ..............................B-1
B.1 Example CR10X Program............................................................... B-1
B.2 Edlog Programming for Long Lead Lengths................................... B-9
Figures
5-1. Polynomial error curve (Edlog dataloggers only)................................ 3
5-2. Thermistor interchangeability limits ................................................... 4
6-1. Mounting kit components.................................................................... 5
6-2. Nuts and lock washers on mounting bolt............................................. 5
6-3. BlackGlobe fitting and cable alignment .............................................. 6
6-4. BlackGlobe mounted to a crossarm (front view)................................. 7
6-5. BlackGlobe mounted to a crossarm (back view) ................................. 7
Tables
5-1. Thermistor Interchangeability Specification ....................................... 3
5-2. Polynomial Error ................................................................................. 3
7-1. Wiring Diagram for Campbell Scientific Dataloggers ........................ 8
A-1. Sample use of WBGT Index............................................................ A-1
B-1. Polynomial Coefficients .................................................................. B-7
B-2. Actual Temperature, Sensor Resistance, and Computed
Temperature................................................................................. B-7

BlackGlobe Temperature Sensor for
Heat Stress
1. Introduction
The BlackGlobe Temperature Sensor for Heat Stress (BlackGlobe) measure
radiant temperature. This measurement, along with the measurement of
ambient air and wet-bulb temperatures, is used to calculate the wet-bulb globe
temperature (WBGT). The WBGT index combines the effects of temperature,
humidity, radiant heat, and wind into one single index employed to express
environmental heat stress. The measurement of heat stress is important
because loss of physical and mental efficiency occurs under definable degrees
of heat stress. Severe heat stress can lead to fatigue, exhaustion and possibly
even disability or death.
Before installing the BlackGlobe, please study
•Section 2, Cautionary Statements
•Section 3, Initial Inspection
2. Cautionary Statements
•The BlackGlobe is a precision instrument. Please handle it with care.
•The black outer jacket of the cable is Santoprene® rubber. This
compound was chosen for its resistance to temperature extremes, moisture,
and UV degradation. However, this jacket will support combustion in air.
It is rated as slow burning when tested according to U.L. 94 H.B. and will
pass FMVSS302. Local fire codes may preclude its use inside buildings.
•Do not use the BlackGlobe with long lead lengths in an electrically noisy
environment.
3. Initial Inspection
•Upon receipt of the BlackGlobe, inspect the packaging and contents for
damage. File damage claims with the shipping company. Immediately
check package contents against the shipping documentation (see Section
3.1, Ships With List). Contact Campbell Scientific about any
discrepancies.
•The model number and cable length are printed on a label at the
connection end of the cable. Check this information against the shipping
documents to ensure the expected product and cable length are received.
3.1 Ships With List
•(4) 7362 8 inch Wire Ties
•(1) 29956 BlackGlobe Mounting Kit
•ResourceDVD
1

BlackGlobe Temperature Sensor for Heat Stress
4. Overview
The BlackGlobe uses a thermistor inside a 15.24 cm (6 in) hollow copper
sphere, painted black to measure radiant temperature. This measurement along
with the measurement of ambient air and wet-bulb temperatures may be used to
calculate the WBGT index, which is sometimes referred to as the Humidex.
Sensor cable length is specified at the time of order. Do not exceed 1000 feet
of cable.
To calculate the wet-bulb globe thermometer index (WBGT), the measurement
of the BlackGlobe (radiant heat), wet-bulb (evaporative heat), and ambient air
(dry-bulb) temperatures are required. The wet-bulb temperature can be
calculated using air temperature and relative humidity if a wet-bulb
thermometer is not available. See Section 7.2, Calculations.
5. Specifications
Temperature Measurement Range: –5° to +95°C
Temperature Survival Range: –50° to +100°C
Thermistor Interchangeability Error: Typically < ±0.2°C over 0°C to 70°C
and ±0.3 at 95°C
Polynomial Linearization Error: < ±0.5°C over –7°C to +90°C
Near Normal Emittance: 0.957
Maximum Cable Length: 305 m (1000 ft)
The black outer jacket of the cable is Santoprene@ rubber. This
compound was chosen for its resistance to temperature extremes,
moisture, and UV degradation. However, this jacket will support
combustion in air. It is rated as slow burning when tested
according to V.L. 94 H.B. and will pass FMVSS302. Local fire
codes may preclude its use inside buildings.
NOTE
5.1 Accuracy
The overall probe accuracy is a combination of the thermistor’s
interchangeability specification, the precision of the bridge resistors, and the
Steinhart-Hart equation error (CRBasic dataloggers) or the polynomial error
(Edlog dataloggers). In a worst case, all errors add to an accuracy of ±0.3°C
over the range of –3° to 90°C and ±0.7°C over the range of –5° to 95°C. The
major error component is the interchangeability specification of the thermistor,
tabulated in TABLE 5-1 and plotted in FIGURE 5-2. For the range of 0° to
50°C, the interchangeability error is predominantly offset and can be
determined with a single point calibration. Compensation can then be done
with an offset entered in the measurement instruction. The bridge resistors are
0.1% tolerance with a 10 ppm temperature coefficient. Polynomial errors are
tabulated in TABLE 5-2 and plotted in FIGURE 5-1.
2

BlackGlobe Temperature Sensor for Heat Stress
TABLE 5-1. Thermistor
Interchangeability Specification
Temperature (°C)
Temperature
Tolerance (±°C)
−5 0.14
0 to +70 0.10
+85 0.25
+95 0.35
TABLE 5-2. Polynomial Error
–5°to +95°< ±0.5°C
–3°to +90°< ±0.1°C
FIGURE 5-1. Polynomial error curve (Edlog dataloggers only)
3

BlackGlobe Temperature Sensor for Heat Stress
Thermistor Interchangeability Limits
T
error
_therm_pos
T
error
_therm_neg
0
T
0.3
0.25
0.2
0.15
0.1
0.05
-0.05
-0.1
-0.15
-0.2
-0.25
-0.3-5 10 25 40 55 70 85 100
FIGURE 5-2. Thermistor interchangeability limits
6. Installation
6.1 Siting
The BlackGlobe must be mounted in a location that will not be shadowed and
is representative of the environmental conditions to be measured.
6.2 Assembly and Mounting
Tools required for installing on a tripod or tower:
•Adjustable end wrench or 7/16 in. and 1/2 in. open end wrench
•Small screwdriver provided with the datalogger
•Small pair of diagonal-cutting pliers
•UV resistant cable ties provided with the BlackGlobe
6.2.1 Mounting the BlackGlobe on the Mounting Arm
The BlackGlobe and mounting kit (pn 29956) requires some assembly before
installation. The mounting kit comes with (see Figure 6.1):
•Mounting arm
•Mounting bolt
•Two lock washers
•Two nuts
•Two pipe clamps (not used when mounted to a horizontal pipe cross
arm)
•U-bolt with associated nuts and washers
4

BlackGlobe Temperature Sensor for Heat Stress
Mounting Ar
m
Pipe Clamp Slot
N
uts
Lock Washers
Pipe Clamps U-bolt Mounting Bol
t
FIGURE 6-1. Mounting kit components
1. Place the mounting bolt through the hole in the mounting arm as shown in
FIGURE 6-2.
2. Slide one of the lock washers against the mounting arm.
3. Thread both nuts about half way down the bolt and then slide on the last
lock washer. The hardware should be arranged as shown in FIGURE 6-2.
FIGURE 6-2. Nuts and lock washers on mounting bolt
5

BlackGlobe Temperature Sensor for Heat Stress
4. Tighten down the nut closest to the mounting arm so the bolt is held firmly
in place.
5. Thread the BlackGlobe fitting onto the bolt. Thread it as far down as it
will go, but you may have to back it off a bit. The cable gland and cable
should align with the mounting arm as shown in FIGURE 6-3.
6. Tighten down the nut closest to the BlackGlobe fitting. The BlackGlobe
and mounting bolt should not move when the all the hardware is tightened
down.
Cable Gland
FIGURE 6-3. BlackGlobe fitting and cable alignment
6.2.2 Mounting the BlackGlobe Assembly on a Horizontal Crossarm
The BlackGlobe assembly must be mounted on a horizontal crossarm.
1. Position the sensor so that the cable gland is facing down (FIGURE 6-3).
2. Use the mounting hardware supplied to hold the sensor on the horizontal
crossarm. FIGURE 6-4 and FIGURE 6-5 show a BlackGlobe mounted on
a crossarm by using the U-bolts.
3. Use the wire ties provided with the unit to secure the cabling to the
crossarm.
4. Leave a small loop of cable at the cable entry into the sensor to act as a
drip line for any condensed moisture or rain (FIGURE 6-4).
6

BlackGlobe Temperature Sensor for Heat Stress
FIGURE 6-4. BlackGlobe mounted to a crossarm (front view)
FIGURE 6-5. BlackGlobe mounted to a crossarm (back view)
7. Operation
7.1 Wiring
The wiring diagram for the BlackGlobe to a Campbell Scientific datalogger is
given in TABLE 7-1. Temperature is measured with one single-ended input
channel and a voltage excitation channel. Multiple probes can be connected to
the same excitation channel (the number of probes per excitation channel is
physically limited by the number lead wires that can be inserted into a single
voltage excitation terminal, approximately six).
7

BlackGlobe Temperature Sensor for Heat Stress
TABLE 7-1. Wiring Diagram for Campbell Scientific Dataloggers
Color
Description
CR800
CR850
CR5000
CR3000
CR1000
CR9000(X)
CR510
CR500
CR10(X)
21X
CR7
CR23X
Black Voltage
Excitation
Switched
Voltage
Excitation
Switched
Excitation
Switched
Excitation
Red Temperature
Signal
Single-Ended
Input
Single-Ended
Input
Single-Ended
Input
Purple Signal Ground AG
Clear Shield G
7.2 Calculations
7.2.1 Wet-Bulb Globe Thermometer Index (WBGT)
To calculate the WBGT index, a measurement of the BlackGlobe (radiant
heat), wet-bulb (evaporative heat), and ambient air (dry-bulb) temperatures are
required (Equation 1). In the approach discussed here, air temperature and
relative humidity measurements are used to calculate the actual vapor pressure,
and a dewpoint temperature is used to calculate the wet-bulb temperature.
Air temperature and relative humidity (%) measurements required for this
calculation can be made by a variety of sensors. In the examples shown in
Section 7.3, Programming, the HC2S3 is used.
Ultimately,
WBGT = (0.2 ×BlackGlobe Temp) + (0.7 ×Wet-Bulb Temp) + (0.1 ×Dry-
Bulb Temp) (1)
Dewpoint and Wet-Bulb temperature units include: °C, °F, °K
7.2.2 Dewpoint
Equation 2 is used to calculate dewpoint.
Td = (241.88*ln(P/0.61078))/(17.558-ln(P/0.61078)) (2)
where
Td= dewpoint (°C)
P = vapor pressure (kPa)
8

BlackGlobe Temperature Sensor for Heat Stress
The equation is an inverse of a version of Teten’s equation (Tetens, 1930),
optimized for dewpoints in the range –35° to 50°C, and is accurate to within
plus or minus 0.1°C within that range.
7.2.3 Vapor Pressure
Vapor pressure is calculated by the datalogger using Equation 3.
P = RH*Psw/100 (3)
where
RH = relative humidity (%)
Psw = saturation vapor pressure (kPa) over water
7.2.4 Saturated Vapor Pressure
Saturation vapor pressure over water is calculated by the datalogger using
Equation 4.
Psw (kPa) = 0.1*(6.107799961 + T(4.436518521 ×10–1 + T(1.428945805 ×
10–2 + T(2.650648471 ×10–4 + T(3.031240396 ×10-6 + T(2.034080948 ×10–8
+ 6.136820929 ×10–11 ×T)))))) (4)
where
T = air temperature (dry-bulb temperature) (°C)
7.2.5 Wet-Bulb
Wet-bulb is derived using an iterative process. The wet-bulb temperature lies
somewhere between the dry-bulb temperature (air temperature) and the
dewpoint temperature. The datalogger uses Equation 5 to calculate vapor
pressure using the dry-bulb temperature and a wet-bulb temperature estimate:
P = Pw–(0.000660*(1+0.00115*Tw)*(T–Tw)*SP) (5)
where
Pw= saturation vapor pressure (kPa) at the wet-bulb temperature (°C)
Tw= wet-bulb temperature (°C)
T = air temperature (dry-bulb temperature) (°C)
SP = standard air pressure (kPa) at the user entered elevation
The resulting vapor pressure is compared to the true vapor pressure (see above)
and the difference determines the next wet-bulb temperature estimate. The
process repeats until the difference between the current wet-bulb temperature
estimate and the previous wet-bulb temperature estimate is only plus or minus
0.01°C. The datalogger thus derives the wet-bulb temperature.
9

BlackGlobe Temperature Sensor for Heat Stress
7.2.6 Mean Site Barometric Pressure Calculation (SP_kPa)
The wet-bulb instruction needs mean barometric pressure which is closely
related to elevation of the site. U.S. Standard Atmosphere and dry air were
assumed when Equation 6 was derived (Wallace & Hobbes, 1977).
⎪
⎭
⎪
⎬
⎫
⎪
⎩
⎪
⎨
⎧⎟
⎠
⎞
⎜
⎝
⎛−−−=
25328.5
69231.44307
11325.101325.101 E SP
kPa (6)
The value of SPkPa is in kilopascals and the site elevation, E, is in meters.
Use Equation 7 to convert feet to meters.
()
(
)
ft/m
ftE
mE 281.3 =(7)
The value for SPkPa must be put into the datalogger program.
7.3 Programming
7.3.1 Example CR1000 Program
The example includes measurements of the BlackGlobe temperature, and the
calculation of wet-bulb temperature and wet-bulb globe temperature.
Measurements of air temperature and relative humidity are supplied by an
HC2S3 in this example. Calculations for dewpoint, wet-bulb, and wet-bulb
globe temperature are also included.
'CR1000 Series Datalogger
'Program: BlackGlobe.CR1
'Declare constants
'Mean site barometric pressure at 1357.58 meters.
'CHANGE THIS VALUE TO MATCH YOUR ELEVATION.
Const SP_kPa = 86.04377
'Declare Public Variables
'Datalogger variables.
Public PnlTempC 'Datalogger panel temperature
Units PnlTempC=Deg C
Public Batt_Volt 'Datalogger battery voltage
Units Batt_Volt=VDC
'BlackGlobe variables.
Public BGTemp_C 'BlackGlobe temperature
Units BGTemp_C=Deg C
'Rotronic HC2S3 variables.
Public AirTempC 'Air temperature
Units AirTempC=Deg C
Public AirRH 'Humidity
Units AirRH=%
'Calculated variables.
Public DewPnt_C 'Dewpoint temperature
Public WetBlb_C 'Wet-bulb temperature
Public WBGT_C 'Wet-bulb globe (HUMIDEX) temperature
Dim SVP_kPa
Dim VP_kPa
10

BlackGlobe Temperature Sensor for Heat Stress
Dim UpperTmp
Dim LowerTmp
Dim old_wbT, new_wbT
Dim WB_VP_kPa, Diff_VP_kPa
Dim Diff_wbT
'Define Data Tables
'Hourly data table.
DataTable (Hourly,1,-1)
DataInterval (0,1,Hr,10)
Average (1,AirTempC,FP2,False)
Sample (1,AirRH,FP2)
Average (1,DewPnt_C,FP2,False)
Average (1,WetBlb_C,FP2,False)
Average (1,WBGT_C,FP2,False)
EndTable
'Daily datalogger status table.
DataTable (Daily,True,-1)
DataInterval (0,1,Day,10)
Maximum (1,Batt_Volt,FP2,False,False)
Minimum (1,Batt_Volt,FP2,False,False)
Maximum (1,PnlTempC,FP2,False,False)
Minimum (1,PnlTempC,FP2,False,False)
EndTable
'Main Program
BeginProg
Scan (5,Sec,3,0)
PanelTemp (PnlTempC,250)
Battery (Batt_Volt)
'Rotronic HC2S3 powered up all the time.
VoltSe (AirTempC,1,mV2500,1,0,0,_60Hz,0.1,-40)
VoltSe (AirRH,1,mV2500,2,0,0,_60Hz,0.1,0)
If (AirRH >= 100) AND (AirRH <= 108) Then AirRH = 100
SatVP (SVP_kPa,AirTempC)
VP_kPa = SVP_kPa * AirRH/100
DewPoint (DewPnt_C,AirTempC,AirRH)
If (DewPnt_C > AirTempC) Or (DewPnt_C = NAN) Then DewPnt_C = AirTempC
UpperTmp = AirTempC
LowerTmp = DewPnt_C
'BlackGlobe wired to SE channel 3 and excitation channel VX1.
Therm108 (BGTemp_C,1,3,Vx1,0,_60Hz,1.0,0)
'Loop to find wet-bulb temperature.
Do
old_wbT = new_wbT
new_wbT = ((UpperTmp - LowerTmp)/2) + LowerTmp
WetDryBulb (WB_VP_kPa,AirTempC,new_wbT,SP_kPa)
Diff_VP_kPa = WB_VP_kPa - VP_kPa
Diff_wbT = ABS (old_wbT - new_wbT)
If Diff_VP_kPa > 0 Then
UpperTmp = new_wbT
Else
LowerTmp = new_wbT
EndIf
If Diff_wbT < 0.01 Then ExitDo
Loop
'Wet-bulb temperature.
WetBlb_C = new_wbT
'Calculate Wet-Bulb Globe (HUMIDEX) temperature.
WBGT_C = (0.1 * AirTempC) + (0.2 * BGTemp_C) + (0.7 * WetBlb_C)
'Call data storage tables.
CallTable Hourly
CallTable Daily
NextScan
EndProg
11

BlackGlobe Temperature Sensor for Heat Stress
7.4 Long Lead Lengths
If the BlackGlobe has lead lengths greater than 300 feet, a longer settling time
before the measurement is made is required. For CRBasic loggers, the 60 and
50 Hz integration options include a 3 ms settling time; longer settling times
also can be entered into the Settling Time parameter. In Edlog, use the DC
Half Bridge Instruction (Instruction 4) with a 2 ms delay to measure the
temperature.
Do not use the BlackGlobe with long lead lengths in an
electrically noisy environment.
CAUTION
8. Maintenance
The BlackGlobe requires minimal maintenance. Check monthly to ensure the
sphere is free from dirt and debris. Clean with water and soft cloth if
necessary. Do not use solvents as they may dissolve the paint.
9. References
Lowe, P.R. 1977. J. Appl. Meteor., 16:100-103
Tetens, O. 1930. Z. Geophys., 6:297
Wallace, J.M. and P.V. Hobbes, 1977: Atmospheric Science: An Introductory
Survey, Academic Press, pp. 59 – 61
12

Appendix A. The Theory of BlackGlobe
Temperature and Heat Stress
The Wet-Bulb Globe Temperature Index (WBGT) combines the effects of
temperature, humidity, radiant heat, and wind into one single index employed
to express environmental heat stress. Loss of physical and mental efficiency
occurs under definable degrees of heat stress. Severe heat stress can lead to
fatigue, exhaustion and possibly even disability or death. Personnel can
increase their resistance to heat stress by acclimatizing gradually to hot
environments and by maintaining a good water and salt balance.
Heat stress can be reduced by decreasing the lengths of exposure and
decreasing the workload of individuals under heat stress. Situational factors
such as the type of clothing worn, the type of work performed, the
psychological effects of stress, and the availability of fluids can also affect the
assessment of heat stress. These factors are not easily quantified, and so the
individual in a given situation must estimate their significance. Environmental
factors such as temperature, humidity, and wind are more easily measured to
assess heat stress. TABLE A-1 provides some guidelines for using the WBGT
index.
TABLE A-1. Sample use of WBGT Index
Readings Guidelines
WBGT Index
Reading 26 – 27.5
Precautions should be taken. Water intake should be a
minimum of 0.5 liters/hr. The work/rest cycle for an
acclimatized person should be 50/10 min/hr.
WBGT Index
Reading 27.5 – 29
Increased water intake should be emphasized. Water
intake should be 0.5 to 1 liters/hr. The work/rest cycle
for an acclimatized person should be 50/10 min/hr.
WBGT Index
Reading 29 – 31
Increased supervision of personnel performing physical
activity is required. Water intake should be 1 to 1.5
liters /hr. The work/rest cycle for an acclimatized person
should be 45/15 min/hr.
WBGT Index
Reading 31 – 32
Physical activity should be limited to a maximum of 6
hours per day for fully acclimatized personnel. Water
intake should be 1.5 to 2 liters/hr. The work/rest cycle
for an acclimatized person should be 30/30 min/hr.
WBGT Index
Reading >32
All strenuous activity should be suspended. Water
intake should be a minimum of 2 liters/hr. The
work/rest cycle for an acclimatized person (non-
strenuous activity) should be 20/40 min/hr.
A-1

Appendix A. The Theory of BlackGlobe Temperature and Heat Stress
A-2